This invention relates to an electrochromic (hereinafter referred to as xe2x80x9cECxe2x80x9d) mirror using an EC device which is used for a dimming mirror, a dimming window, and so on, and more particularly, to a reflecting film structure of a solid type EC mirror in which an electrolyte is made of solid.
An EC device is used for an automobile dimming mirror or dimming window by utilizing its capability of varying optical transmittance. As a prior art solid type EC mirror, known in the art is one having a structure as shown in FIG. 2. On one surface (i.e., rear surface as viewed from the side on which light is incident) of a transparent glass substrate 2 are laminated a transparent electrode film 4, an EC device 11 consisting of three layers of an anode compound film 6, a solid electrolyte film 8 and a cathode compound film 10, and an Al reflecting electrode film 12. A part of the Al reflecting electrode film 12 constitutes a wiring 12a which extends along an end surface of the EC device 11, and is electrically connected to a cathode side electrode section 18 provided on the glass substrate 2 through a portion of the transparent electrode film 4. The transparent electrode film 4 is separated in upper and lower portions by a slit 15 which is formed in the vicinity of the lower end portion of the EC device 11 by means of, e.g., laser beam cutting. Short-circuiting between an anode side electrode section 17 and the cathode side electrode section 18 through the transparent electrode film 4 is prevented by this slit 15. The slit 15 may theoretically be formed at a location immediately above the lower end of the EC device 11 but, in actuality, the slit 15 is formed at a location which is about 1 mm above the lower end of the EC device 11, having regard to a positioning error in forming the slit 15. Since the slit 15 is seen as a line with a human eye, it is necessary as a product to conceal this slit 15 with a mirror holder. For this reason, the region of about 1 mm from the lower end of the EC device 11 is excluded from the scope of the reflecting mirror as a slit required width 2c. On the other hand, in the upper end portion of the Al reflecting electrode film 12, an insulation width 2d of about 0.5 mm from the upper end of the EC device 11 is provided for preventing forming of the Al reflecting electrode film 12 in contact with the transparent electrode film 4, having regard to a positioning error in forming the Al reflecting electrode film 12. The portion of the insulation width 2d has no function of a reflecting mirror because the Al reflecting electrode film 12 is not formed in this portion. The surface of the Al reflecting electrode film 12 is sealed with a sealing resin 14 which protects the Al reflecting electrode film 12 from outside moisture or soil and thereby prevents corrosion of the Al reflecting electrode film 12 with moisture. On the surface of the sealing resin 14 is mounted a sealing glass 16 for enhancing stability against variations in outside temperature and humidity.
In the structure of the EC mirror shown in FIG. 2, moisture contained in the air tends to permeate into mirror structure through the outer periphery (i.e., surface exposed to the air) of the sealing resin 14 by reason of variations in temperature and humidity. The moisture which has permeated from the sealing resin 14 corrodes the surface of the Al reflecting electrode film 12 which is in contact with the sealing resin 14 and the wiring 12a which is a part of the Al reflecting electrode film 12.
A disadvantage which is caused by corrosion of the Al reflecting electrode film 12 is that a reflection image becomes inaccurate. Another disadvantage is that aluminum becomes an insulating material (Al2O3) by corrosion. By changing of the wiring 12a to an insulating material, electric current which is necessary for coloring and discoloring the EC device 11 can not flow sufficiently and uniformly to the Al reflecting electrode film 12 whereby there occur irregularity in coloring of the EC device and decrease in the coloring and discoloring speeds.
For preventing corrosion of the Al reflecting electrode film 12, it is necessary to form the sealing resin to a sufficient thickness (e.g., about 3 mm) thereby to prevent permeating of moisture accurately. For forming the sealing resin 14 to a sufficient thickness, the EC device 11 and the Al reflecting electrode film 12 must be formed with their outer peripheries being offset sufficiently inwardly (about 3 mm) from the outer peripheral surface of the glass substrate 2 for providing, as the thickness of the sealing resin 14, an offset width 2b of about 3 mm in which the EC device 11 and the Al reflecting electrode film 12 are not formed. For this reason, the outer peripheral portion of the glass substrate 2 of a range including the offset width 2b for providing the sealing resin, the slit required width 2c and insulation width 2d cannot be used as a reflecting surface and a remaining range 2a of an effective field of view is rather narrow. Further, this arrangement requires a mirror holder 3 for concealing the portion excluding the range 2a of the effective field of view has a large width and appears awkward.
It is, therefore, an object of the present invention to provide a solid type EC mirror having an enlarged range of effective field of view by improving resistivity to corrosion of a reflecting electrode film such as an Al reflecting electrode film.
For achieving the above described object of the invention, there is provided an electrochromic mirror comprising a transparent substrate, a first conductive film, an anode or cathode compound film, a solid electrolyte film, a cathode or anode compound film, and a second conductive film, these films being successively laminated on one surface of the transparent substrate, and said second conductive film consisting of a laminate formed by laminating, from the side of the cathode or anode compound film, at least two layers of a high reflecting metal material film and a high corrosion resistant metal film.
According to the present invention, since the high corrosion resistant metal film is formed on the surface of the high reflecting metal material film, moisture contained in the outside air is interrupted by the high corrosion resistant metal film and the high reflective metal material film can thereby be protected from corrosion. The corrosion resistance of the high reflecting metal material film is thereby improved and, as a result, good visibility can be maintained and decrease in the coloring and discoloring function of the EC device can be prevented. Besides, the high corrosion resistant metal film can be formed in a thinner shape than the prior art sealing resin while securing the function of protecting the reflecting film and, therefore, the offset width can be reduced and the range of effective field of view can thereby be enlarged.
The high reflecting metal material film may be made of a semitransparent film. According to this aspect of the invention, reflection by the high reflecting metal material film and the high corrosion resistant reflecting metal film can be obtained and, therefore, a higher reflectance than in the case where only the high corrosion resistant metal film is used can be obtained. Further, since the amount of the high reflecting metal material film used can be reduced, the cost of material can be reduced even when an expensive high reflecting metal material is used.
The high reflecting metal material film may be made of a film which does not transmit light.
In one aspect of the invention, the high corrosion resistant metal film may extend to the transparent substrate or to the vicinity of the transparent substrate along end surfaces of the high reflecting metal material film, the cathode or anode compound film, the solid electrolyte film and the anode or cathode compound film so that the extended portion may be used as a wiring.
In one aspect of the invention, the laminate of the high reflecting metal material film and the high corrosion resistant metal film may extend to the transparent substrate or to the vicinity of the transparent substrate along end surfaces of the cathode or anode compound film, the solid electrolyte film and the anode or cathode compound film so that the extended portion may be used as a wiring.
In both cases, since the wiring made of the high corrosion resistant metal film is hardly corroded, sufficient current necessary for coloring or discoloring the EC device can be caused to flow whereby irregularity in coloring of the EC mirror and reduction in the coloring and discoloring speeds can be prevented.
The electrochromic mirror of the invention may further comprise a sealing resin layer made, for example, of a resin film, epoxy resin or coating provided on the surface of the high corrosion resistant metal film and a sealing substrate made, for example, of glass, plastic or metal provided on the surface of the sealing resin layer. By this arrangement, a high degree of resistance to environmental changes such as abrupt change in temperature and humidity of the outside air and corrosion resistance to moisture can be provided. Since, in this case, corrosion resistance is provided by the high corrosion resistant metal, the sealing resin layer can be made thinner than the prior art one whereby the offset width can be reduced and the range of effective field of view can be enlarged.
In one aspect of the invention, the high reflecting metal material film may contain Sn, Ag, Al or Rh as a principal ingredient.
In still another aspect of the invention, the high corrosion resistant metal film may contain Cr or Ni as a principal ingredient.
Description of preferred embodiments of the invention will be made below with reference to the accompanying drawings.